Is mild hypernatremia an independent predictor of poor clinical outcome in neurocritically ill patients?

We investigated the impact of hypernatremia on mortality of neurocritically ill patients. Among neurosurgical patients admitted to the intensive care unit (ICU) from January 2013 to December 2019, the patients who were hospitalized in the ICU for more than 5 days included. Hypernatremia was defined as the highest serum sodium level exceeding 150 mEq/L observed. Among 1,146 patients, 353 patients (30.8%) showed hypernatremia. Based on propensity score matching, 290 pairs were analyzed. Hypernatremia group had higher rates of in-hospital mortality compared with non-hypernatremia group in overall and matched population ( p < 0.001 and p = 0.001, respectively). In multivariable analysis of propensity score-matched population, moderate and severe hypernatremia were significantly associated with in-hospital mortality (adjusted odds ratio [OR]: 4.58, 95% confidence interval [CI]: 2.15 – 9.75 and adjusted OR: 6.93, 95% CI: 3.46 – 13.90, respectively) compared with the absence of hypernatremia. However, in-hospital mortality was not significantly different between non-hypernatremia and mild hypernatremia groups ( p = 0.720). Interestingly, mild hypernatremia group of matched population showed the best survival rate. Eventually, moderate and severe hypernatremia were associated with poor clinical outcomes in neurocritically ill patients. However, prognosis of the patients with mild hypernatremia was similar with those without hypernatremia.